An autonomous direction-finding and navigation system known as EVA (electronic navigator for drivers) for land vehicles is in development. Calculation of an optimal route from an arbitrary starting point to a freely selectable destination or target is based on a road map stored digitally in memory. The greater the distance between the destination and the starting point, the more manifold the possible ways of reaching it by using the memorized road map. These routes are not all equally good; the optimal route must therefore be ascertained by calculation. The computing time needed for extensive computations may mean that the results are not available to the driver in time; he may already have missed a fork in the road or an intersection where he should have turned.